The wall mount suggestion is a great one, especially if your room is not on a slab. Try three spikes that are squat and look like cones, they can really 'drain' resonance from the plinth. You can also make a sandbox type base for it to sit on top of if you really want to get involved. Just placing a couple little baggies filled with sand on the plinth might tell you something about the effect of damping on your tt. You may enjoy all this fiddling, dont worry, its a common symptom. Have fun.
Damping Rega Table
I have found that even though my Rega 2 table sits on a hard tiled floor,it still resonates quite a bit and sends "tapping" on the plinth right through the speakers.I am considering using "Brown Bread" bitumen sheets under the plinth,as soundproofing.Is this a viable or stupid idea?stefanl